Modify some gc related layout tests to work with Ignition.

third_party/WebKit/LayoutTests/netinfo/gc-unused-listeners.html

Index: third_party/WebKit/LayoutTests/netinfo/gc-unused-listeners.html
diff --git a/third_party/WebKit/LayoutTests/netinfo/gc-unused-listeners.html b/third_party/WebKit/LayoutTests/netinfo/gc-unused-listeners.html
index da73c390937e66afc74a345e28ae58c4fa336f76..e5cda4e75837597004c0c8abd73918e8b30d993c 100644
--- a/third_party/WebKit/LayoutTests/netinfo/gc-unused-listeners.html
+++ b/third_party/WebKit/LayoutTests/netinfo/gc-unused-listeners.html
@@ -16,17 +16,23 @@ var callback = function(e) {
 };
 
 // Add a listener.
-// Do not pass the object directly to observeGC function. This may
+var callbackObserver;
+// Do not pass the object directly to observeGC function. It may
 // remain live on this function's stack preventing GC from collecting
 // it. Accessing the object inside an inner function will prevent any
-// unneeded references on this function's stack.
-var callbackObserver = internals.observeGC((() => {return callback;})());
-connection.addEventListener('typechange', callback);
+// unneeded references on this function's stack. (http://crbug.com/595672/)
+(function() {
+  callbackObserver = internals.observeGC(callback);
+  connection.addEventListener('typechange', callback);
+})();
+
 gc();
 shouldBeFalse('callbackObserver.wasCollected');
 
 // Remove the listener and its callback reference.
-connection.removeEventListener('typechange', callback);
+// Access objects in an inner function to avoid references to objects
+// remaining live on this function's stack frame (http://crbug.com/595672/).
+(() => {connection.removeEventListener('typechange', callback);})();
 callback = null;
 gc();
 shouldBeTrue('callbackObserver.wasCollected');